I would find who it belonged to also. It could have been you that lost it and what if it were for books or something that you really needed and they kept it?
I know it's hard, especially this close to Christmas, but, you will feel better seeing the person get it back.
But that is your choice on what you do.

I know when I was in college if I had found that much money I would have kept it. I would have looked back on that as a mistake though and it probably would have always bothered me.

Try to find the owner and in the case that you make a good effort and no one claims it then you can keep it with a clear conscience. Chances are good that someone will claim it though so don't get your hopes up, but if you return it then you can hold your head high knowing that you did the right thing. I believe in karma. If you do the right thing then you will be better off for it.

I would definitely try to find the owner. I don't know what the law is in most places, but I know that in California, anything over $100 had to be turned in to the police. Law or no law, I wouldn't feel right not trying.

this reminds me of something that happened to my brother once. he was walking out of a grocery store and found a small change purse containing a few hundred dollars, and no i.d..
he didn't even think twice about going into the store and informing the manager of what he had found, and turned in the money with his name and our phone number.
i remember giving him a hard time about it, but all he said was what if it was someone's that really needed it. he couldn't enjoy the money thinking that someone else might be suffering for the loss.
later that afternoon, an old woman called to thank him. she was poor and very ill, and that was all of the money she had to buy groceries and medicine for the month. because of her infirmity, she was only able to make it to the store about once a month, so she would save up for the trip.

there's no big moral here. my brother never won the lottery, or recieved a big reward for something. but his conscience was clear, his karma intact, and he felt pretty good for doing the right thing. that's worth more than a few hundred bucks, imo.

__________________
The past is gone it's all been said.
So here's to what the future brings,
I know tomorrow you'll find better things

You withhold the amount and details about where it was found and anything else. The person who says they lost the money will need to tell you how much, what denomination and any other details (It was in a money clip or had a rubber band around it or they were all brand new crisp bills etc.)